In Islam, term indicating something which is common. Directly translated it means "trodden path." In general, the term sunna does not distinguish between what is good and what is bad.In Sunni Islam the word can be used with at least two different meanings. Its most common usage is denoting the examples, the deeds, sayings and unspoken approval of Muhammad as this has been recorded and systemized in the hadiths. The sunna of Muhammad has generally become considered obligatory by most Muslims.The other meaning of the term is to indicate the basic principles of Islam.The two usages are interconnected, but not synonymous, the second being much wider and all-embracing. Both usages are valid, sometimes the general use is differentiated by making it definite, al-sunna.In Shi'i Islam sunna applies also to the deeds, sayings and approvals of the Imams, up to twelve of them depending on which Shi'i orientation.Sunna represents one of the two literal sources of Muslim Law, Sharia. Whether it is equal in value or inferior to the Koran, is a matter of definition and theology. In several instances, it can be said that the sunna has been used to understand the full meaning of the Koran. But there were with early theologians many stating that when there was disagreement between the Koran and the sunna, sunna could just as well be the correct. However, the founder of the Shafi'i school of Sharia, madhhab, Abu Abdullah ash-Shafi'i claimed that the Koran could not be abrogated by anything but itself.The term "sunna" is used several times in the Koran, in two different contexts. It can either denote the practice of God, or the practice of the old, the forefathers. In connection with God the word has also been translated with "way" or "course." When used in connection with the old, it has also been translated with "example", "course" or "destiny."There are a few passages in the Koran which appears to speaks out against allowing other scriptures to be added as sacred to the Koran:

Koran sura 69: The Catastrophe44 Why if he had invented against us any sayings, 45 we would have seized him by the right hand, 46 then we would have cut his jugular vein...

In the hadiths themselves, especially with one of the later collections, by Darimi, there are several passages which legitimize the sunna of Muhammad, stating among others that "a prohibition by the Prophet of God is equal to a prohibition of God." The validity of Darimi's hadiths is highly questionable.Sunna was a central concept of the Arabian societies prior to the advent of Islam, and it is here that the background for its establishing may be sought. During the first century of post-Muhammadan Islam, practically the only formal work done in Islam was the collecting of the Koran in middle of the 7th century. Few of the regulations and institutions for which Islam today is known, had been established.Before the Muhammadan sunna had been defined and Muslim Law developed, there was naturally ways of dealing with problems, but this sunna was in addition to being based on Koranic commands and the memory of the Muhammadan example, also mixed with foreign influences, individual ideas, ra'y, and even inventions, bid'a.The Muslim administration would grow increasingly sophisticated, but the validity of the regulations was always in jeopardy of being questioned, and for new problems no infallible regulation could usually be found. During the same time efforts of collecting as much material as possible about the life of Muhammad and the earliest Muslims had begun. And as his contemporaries had died out, the challenge of keeping out false stories had become one of the main challenges.The process of change, turning an Islam of limited functions into a fully encompassing system of regulations and attitudes, spanned several generations. Roughly one could say that the collecting of stories, sira, would be followed by the systemizing and quality control of these stories, hadith, in order to be crowned by Muslim Law, Sharia. In reality all these processes started about the same time, in the last decades of the 7th century, but their completion was in the order above.The terms 'sunna' and 'hadith', sometimes even 'sira' are often mixed, simply because their meanings are so close. Some collections of hadiths have also been titled using sunna.